Pigments and particles with unsaturated surface and method of making same



United States Patent-Q PIGMENTS AND PARTICLES WITH UNSATU- RATED SURFACEAND METHOD OF MAK- ING SAME Theodore A. Te Grotenhuis, Olmsted Falls,Ohio, assiguor of twenty percent to The General Tire & Rubber Company,Akron, Ohio, a corporation of Ohio N Drawing. Application October 12,1951, Serial No. 251,152

8 Claims. (Cl. 260-41) The present invention is a continuation in partof my applications Serial No. 714,919, filed December 7, 1946, now U. S.Patent 2,610,167 and application Serial No. 585,824, filed March 30,1945, and it relates to the treatment of fine particles such as pigmentsor fillers and fibers with surface reactive or bonding compoundscontaining organic radicals preferably with unsaturated portions thereonto obtain modified surface characteristics. In particular, the presentinvention relates to the treatment of fine particles with hydroxylreactive unsaturated aliphatic organic compounds such as unsaturatedorganic isocyanate compounds to render the particles organophilic andreactive to polymerizable monomers and vulcanizable polymers and sulfurso as to be compatible with and attracted to organic compounds and toform unsaturated groups on the surface thereof to be interlocked withunsaturated organic materials such as rubber and polymerizablematerials.

It is well-known that various pigments have natural tendencies towardbeing hydrophilic or attracted toward water and easily wet by it, orhydrophobic or non-wettable by water. The majority of pigments andfiller materials such as titanium dioxide, clay, zinc oxide, sulfur,silica, and aluminum oxide tend to be hydrophilic. Carbon black, on theother hand, tends to be somewhat more hydrophobic. These tendencies arewell recognized in the art and their effects readily observed.

Thus, when titanium dioxide, finely divided silica, zinc oxide,magnesia, calcium carbonate, or the like is dispersed in a water-in-oilor oil-in-water emulsion, it tends to go into the water phase. Likewise,with any natural or synthetic latex, or emulsion of polymerizableolefins, these inorganic pigments tend to stay in the water phase. As aresult, there is a tendency for the pigment to be washed away in thewater and it is not compatible with and well dispersed in the organicphase of the emulsion.

It is one object of the present'invention to provide a method oftreating fine particles such as pigments, fibers, and fabrics so thatthey are readily compounded with organic substances and so that they canbe bonded thereto by chemical means such as by possibleinterpolymerization or by sulfur or chemical bridges.

It is another object of the present invention to provide a method oftreatment for fine particles and fibers by which the particles arerendered more readily wettable and interlocked with polymerizableorganic compounds and polymers.

It is still another object-of the present invention to provide a simpleand inexpensive method of improving the ease of dispersion andcompounding of fine particles in organic vehicles and polymers.

Other objects and advantages will become apparent from the followingdescription of my invention.

In accordance with the present invention, I subject the fine particlesto contact with a hydroxyl reactive organic compound such as anunsaturated isocyanate that has at least one NCO group attached to aradical or group selected from the group comprising unsaturatedaliphatic 2,780,612 Patented Feb. 5, 1957 and arylaliphatic groups. Thatis, I subject the particles to contact with an isocyanate having thegeneral formula RNCO where R is selected from alkenyl groups,arylalkenyl groups, etc. Where chemical interlocking is unnecessary andonly hydrophobicity is desired, the isocyanate need not be unsaturatedand alkyl isocyanates may be used. Such alkyl groups are not asdesirable as unsaturated groups however, as bonds cannot be easilyformed between polymers and the surface of the particles. Any of thecommercially available pigments such as titanium dioxide, leadcarbonate, carbon black, magnesia, finely divided silica which hassometimes been referred to as white carbon blac such as the silicas madefrom organic silicates by combustion as well as fillers such as clay,ground wood, lignin, and textile fibers such as those of cotton andglass are susceptible to the treatment and interlocking of the presentinvention.

After treatment of the high surface area material in accordance with thesubject invention, the isocyanate group or water reactive groups of thesilicon compound reacts with the surface of the particles or OH groupchemically attached thereto to form a chemical bond between the surfaceand the unsaturated or organic groups of the organo silicon orisocyanate compound. This renders the particles organophilic orhydrophobic and non-wettable by water. It greatly improves theirdispersion in organic vehicles, their compatibility with resins andresin forming materials, and their efiectiveness in water emulsions, andpermits chemical interlocking of the surface of the pigment or fiberwith unsaturated polymers such as diolefinic rubbers as well as withpolymerizable unsaturated compounds such as styrene. Particles treatedin accordance with the subject invention and incorporated'in arylvinylor olefinic monomeric polymerizable materials such as styrene,methylmethacrylate, or vinyl chloride, give stronger polymers with someof the particles apparently interlocked therein. Likewise, particlesincorporated in unsaturated polymers such as any of the natural orsynthetic rubbers, unsaturated polyesters, and to some extent evensilicon elastomers give better tougher compounds.

The subject invention is especially useful in work with water emulsionseven though the organic groups are saturated. vIn any water-in-oil orwater-in-resin or resinin-water emulsion the particles tend to wash intothe water phase or remain near the interface between the two phases.Thus with an oil-in-water type of emulsion of a film forming materialsuch for example as a resin solution when the emulsion is coagulated andprecipitated, many of the pigments and filler particles, being in thewater phase, tend to keep the particles from coalescing to a film orsolid mass. When the pigments and filler particles are treated to renderthem organophilic, however, they go into organic film forming materialand unite therewith and do not hinder film forming properties in thismanner with the result that glossy pigmented films are produced.

In the case when emulsion paints comprising resin-inwater emulsions arespread to dry, ordinary pigments go into the water phase so that in thedried paint they have very poor bond with the resin, and a porous paintresults with poor washing resistance. Pigments with organic reactionproducts of the organic isocyanates or organo silicons thereon, however,go into the resin phase and as the paint dries, unite with the resin togive a firm, smooth water resistant film.

When the pigment of particle and particularly a high surface areapigment is to be used as a reinforcing agent for a polymer of apolymerizable monomer such as one or more of the polymerizablemono-olefinic compounds or when it is to be incorporated into anunsaturated polymer such as a rubber or certain polyesters, unsaturatedgroups on the pigment surface are highly desirable for interlocking andobtaining reinforcement and accordingly unsaturated aliphatic organicgroups in the treating compound should be present for best results.

The pigments or particles are modified in accordance with the inventionby subjecting the dry fine particles to an unsaturated organicisocyanate having a NCO group, or by dissolving the isocyanate orcompound in an inert dry organic solvent free of hydroxyl, amino, andcarboxyl groups such as ether, carbon tetrachloride, toluene, and thelike and shake the two together for a brief period of time, such as aminute or more and draining off the solvent, and drying the particles.In the alternative, I can subject the particles to the vapor from themore volatile isocyanates such as methyl isocyanate, vinyl isocyanate,and phenyl isocyanate. It is sometimes advisable to heat the particlesand isocyanate under vacuum or reduced pressure to thoroughly vaporizeit.

Various isocyanates can be utilized. For example, I can use alkylisocyanates such as methyl, ethyl, chlorethyl, and isobutyl isocyanate,or ary] isocyanates such as phenyl isocyanate CHsCsH4NCO or alkylenylisocyanates such as chlorethylenyl, vinyl, and propenyl or allylisocyanate and their homologues.

The following examples illustrate the present invention in more detail.

Example 1 100 grams of unbeaded carbon black are subjected to agitationin the presence of a vapor from about grams of a mixture of methyl andethyl isocyanate. The agitation is continued for around ten minutes toallow for a thorough penetration of the vapor. The carbon black thustreated has much less tendency to be wet by water and much greatertendency to be wet by hydrocarbon organic solvents.

When in the above example, vinyl isocyanate is substituted for themethyl and ethyl mixture the black has similar characteristics but alsohas unsaturated groups on the surface for interlocking with unsaturatedorganic compounds and vulcanizing agents such as sulfur.

Example 2 100 grams each of titanium dioxide and a finely dividedsilica, which sometimes has been termed White carbon black having asurface area of more than 50 square meters per gram is separatelysubjected to agitation in the presence of grams of vinyl isocyanate in aclosed dry vessel under sulliciently reduced pressure to insure thepresence of the isocyanate vapor. continued for around ten minutes toallow for a thorough penetration of the vapor. Both the titanium dioxideand the silica thus treated have much less tendency to be wet by waterand a much greater tendency to be wet by hydrocarbon organic solventsand has unsaturated groups for attachment to unsaturated materialseither by sulfur bridging or by polymerization interlocking.

Example 3 The methyl and ethyl isocyanate compounds of Example l aresubstituted by allyl isocyanate dissolved in 200 grams of anhydroustoluene. 100 grams of carbon black is thoroughly wet by the solutionthus formed and after evaporation of the solvent is found to have anexceedingly strong afiinity for organic hydrocarbons.

Example 4 300 grams of finely divided silica having a surface area ofover 80 square meters per gram and treated with allyl isocyanate as wasthe carbon black of Example 3 and ground in a ball mill withapproximately 100 grams of water containing 30 grams of Daxad (acondensation product of naphthaline sulfonic acid and formaldehyde). Theaqueous dispersion thus prepared is mixed with about 1800 parts ofrubber latex containing 50% of rubber The agitation is I solids, about 5parts of zinc oxide and 1 part of sulfur. Films formed from thecompounded latex mixture after drying and vulcanization have highstrength. The latex mixture upon coagulation and slight mastication isfound to have the silica dispersed therein, suitable for inter actionwith the rubber hydrocarbon as evidenced by a reinforcing effect similarto that of carbon black upon cure of the mixture.

The rubber latex of the above example may be substituted in whole or inpart with a latex of natural or synthetic rubber or resinous polymer andparticularly a sulfur vulcanizable or synthetic rubber or the like, ormixtures of; these materials to produce articles having the desirablecharacteristics of various articles of manufacture.

Example 5 5 parts of titanium dioxide treated as in Example 2 isdispersed into 100 parts by weight of styrene containing about /2 partof benzoyl peroxide and /2 part of soya lecithin by passing the mixturethrough a colloid mill. The dispersion thus prepared is stronglyagitated to maintain a suspension (fine droplets of styrene throughoutthe aqueous phase). The aqueous fluid is maintained in a completelyfilled vessel under super atmospheric pressure for several hours withsaid agitation until polymerization of the styrene in suspended form ishad. The polystyrene thus obtained upon coagulation and drying of thesuspension is desirable for use as a molding powder and in thepreparation of plastic articles or for solution in the preparation of acoating composition.

Example 6 20 parts of titanium dioxide, preferably treated as in Example2, is dispersed in about 125 parts of a creamy viscosity solutionconsisting of an alkyd resin, such as glycerol phthalate or tung oilmodified glycerol phthalate resin, and dissolved in a volatile solventsuch as a mixture of xylene and butyl acetate containing a small amountof a high boiling ester, such as dibutyl phthalate, diorphotoluylphthalate, etc. The dispersion thus obtained is emulsified in 1 timesits volume in an aqueous solution containing 3% gelatin and 3% ammoniumhydroxide. The emulsion thus prepared is especially desirable as acoating or coloring composition.

Example 7 100 grams of matted glass fiber is subjected to the vaporfrom10 grams of allyl isocyanate in benzene at slightly elevatedtemperature. The fibers are maintained in contact with the isocyanatefor approximately minutes and then withdrawn and dried. These fibers arethen Wetted with a polymerizable polyester compound comprising 200 partsof monomeric styrene and 200 parts of a syrupy condensation product of100.1 part of ethylene glycol or diethylene glycol, 80 parts of adipicacid and parts of maleic anhydride. The wetted fibers are molded andallowed to set up in the mold in the usual manner. The resultingcompound is found to have increased water resistance and strengthcompared to compounds made from untreated glass fibers.

In this example, other textile fibers such as cotton and rayon fibersmay be substituted for the glas fibers.

Example 8 50 parts of carbon black treated with methyl and ethylisocyanates as utilizing the procedure of Example 3, except that theisocyanates were not unsaturated, are dispersed in 15 parts of resinvarnish, 10 parts of gilsonite varnish, 430 parts new zinc oil(petroleum oil) and about 5 parts of a solution of a mixture consistingof 1 part of barium naphthenate and parts of polyisobutylene by grindingthe ingredients together in a ball mill for a relatively short time. Theink thus obtained has an unusual degree of jet'ness showing a completedispersion of carbon black in the organic vehicle.

In the above examples, the unsaturated isocyanates may be substituted byother unsaturated isocyanates.

The pigments and fibers of the above examples may be substituted inwhole or in part by other pigments and fibers. The solvent used for thei. e. toluene, benzene, and the like may be substituted by otheranhydrous solvents which do not contain the hydroxyl, amine, or othergroup for reaction with isocyanates and hydroxyl reactive siliconcompounds.

The styrene in the above examples may be substituted in whole or in partby other polymerizable olefinic ma terials such as substituted styrenes,mixtures of styrenes, and alpha methylstyrene or their polymerizablederivatives and homologues, acrylic and methacrylic esters, amids andnitriles, and to some extent vinyl and vinylidene esters etc. Thepolyester of Example 8 may be substituted by other unsaturatedpolyesters to obtain particular properties desired.

It is to be understood that in accordance with the provisions of thepatent statutes, variations and modifications of the specific inventionherein shown and described for purposes of illustration may be madewithout departing from the spirit of the invention.

What I claim is:

-1. A particle of an inorganic solid which is normally hydrophilic butwhich is modified by having bonded to the surface thereof unsaturatedhydrocarbon groups from an aliphatic isocya-nate, said hydrocarbongroups being bonded through the residue from the reaction of a NCO groupof said isocyanate with the surface of said particle.

2. A solid body comprising a solid, synthetic organic polymer of anolefinic monomer, having dispersed therethrough inorganic solidparticles, the surface of which is chemically united to the said solidpolymer through the residue from the reaction of an isocyanate group ofan organic isocyanate with a hydroxyl group on the surface of saidparticles.

3. A solid synthetic organic polymer of a polymerizable material havingolefinic unsaturation, having distributed therein a reinforcing materialselected from the group consisting of powders and fibers which arebonded to said high polymer through a linkage formed by the residue fromthe reaction of said polymerizable material, and unsaturated aliphaticgroups bonded to the surface of the reinforcing material through theresidue from the reaction of an isocyanate having a carbon-to-carbondouble bond with said reinforcing material.

4. A solid in situ solidified synthetic organic polymer of apolymerizable olefinic compound having distributed therethrough areinforcing material selected from the group consisting of powders andfibers which normally have hydroxyl groups on their surfaces, but whichare modified by having olefinic groups of two to three inclusive carbonatoms bonded to the surface thereof through the residue from thetreatment of the surface of said reinforcing material with anunsaturated organic isocyanate having carbon-to-carbon double bonds,whereby said polymer is chemically bonded to said reinforcing materialthrough the interaction of said polymerizable material with the saidolefinic groups on the said reinforcing material.

5. In a method for bonding together particles selected from the groupconsisting of inorganic powders and fibers normally having hydroxylgroups on their surfaces, the steps which comprise treating saidparticles with an olefinically unsaturated organic isocyauate to bond anunsaturated group to the surface of said particles through the residuefrom the reaction of said isocyanate on the surface of said particles,incorporating the thu treated particles into a polymerizable syntheticorganic material having olefinic groups for interaction with said vinylgroup during the polymerization of said material to form a chemical bondtherewith, and permitting said material to polymerize in contact withsaid particles.

6. in a method for forming strongly bonded composite articles comprisingan inorganic powder having particles bonded together by a solidsynthetic organic polymer of a polymerizable olefinic compound, thesteps which comprise incorporating into a solid synthetic organicplastic mixture containing olefine groups for entering intopolymerization, inorganic particles having vinyl groups bonded to thesurface thereof through the residue from the treatment of said particleswith a vinyl isocyanate, and thereafter treating said plastic mixture tochange it from the plastic to the nonplastic state, and to react saidmaterial with said vinyl groups, thereby chemically bonding saidparticles to said mixture, said powder normally having hydroxyl groupson its surface.

7. An inorganic powder normally having hydroxyl groups thereon but whichis modified by having vinyl groups chemically bonded to the surfaceportion thereof through the residue from the treatment of surfaces ofsaid powder with an unsaturated organic isocyanate havingcarbon-to-carbon double bonds and an -NCO group, said vinyl groups beingattached directly to a carbon atom present in said organic isocyanate.

8. In a process of preparing high surface area particles selected fromthe group consisting of powders and fibers having unsaturated groupsover surface portions thereof for reaction with unsaturated materialsand vulcanizing agents during polymerization and vulcanization, thesteps which comprise contacting the dry surfaces of said particles withan unsaturated isocyanate having an NCO group, and permitting saidisocyanate and surfaces to remain in contact until the surfacecharacteristics are modified, said particles normally carrying hydroxylgroups on their surface.

References Cited in the file of this patent UNITED STATES PATENTS284,289 Fleming Sept. 4, 1883 2,196,033 Schuhmann Apr. 2, 1940 2,273,040Iler Feb. 17, 1942 2,284,895 Hanford et al. June 2, 1942 2,358,683Bradshaw Sept. 19, 1944 2,439,689 Hyde Apr. 13, 1948

3. A SOLID SYNTHETIC ORGANIC POLYMER OF A POLYMERIZABLE MATERIALS HAVINGOLEFINIC UNSATURATION, HAVING DIS TRIBUTED THEREIN A REINFORCINGMATERIAL SELECTED FROM THE GROUP CONSISTING OF POWDERS AND FIBERS WHICHARE BONDED TO SAID HIGH POLYMER THROUGH ALINKASGE FROMED BY THE RESIDUEFROM THE REACTION OF SAID POLYMERIZABLE MATERIAL, AND UNSATURATEDALIPHATIC GROUP BONDED TO THE SURFACE OF THE REINFORCING MATERIALTHROUGH THE RESIDUE FROM THE REACTION OF AN ISOCYANATE HAVING ACARBON-TO-CARBON DOUBLE BOND WITH SAID REINFORCING MATERIAL.